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Motion In Straight Line

Question
CBSEENPH11020537
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A ship A is moving Westwards with a speed of 10 kmh-1 and a ship B 100km  south of A, is moving Northwards with a speed of 10 kmh-1. The time after which the distance between them becomes shortest is

  • 0 h

  • 5 h

  • 5 square root of 2 space straight h
  • 10 square root of 2

Solution

B.

5 h

It is clear from the diagram that the shortest distance between the ship A and B  is PQ.

Here comma space sin space 45 degree space equals space PQ over OQ rightwards double arrow space PQ space equals space 100 space straight x fraction numerator 1 over denominator square root of 2 end fraction space equals space 50 square root of 2 space straight m Also comma space straight v subscript AB space equals space square root of straight v subscript straight A superscript 2 plus straight v subscript straight B superscript 2 end root space equals space square root of 10 squared plus 10 squared end root space equals space 10 square root of 2 space km divided by straight h So comma space time space taken space ofr space to space reach space shortest space path space is space straight t equals PQ over straight v subscript AB space equals space fraction numerator 50 square root of 2 over denominator 10 square root of 2 end fraction space equals space 5 straight h

Some More Questions From Motion in Straight Line Chapter

Can you think of physical phenomena involving the moon in which moon cannot be treated as particle?

A train is crossing the bridge. Can it be taken as a particle?

Can a train be taken a particle? Give an example in support of your answer.

 A particle is moving along curved line in space. Is the motion one dimensional?

State which of the following are examples of one, two or three dimensional motion: 

(a) A kite flying in the sky.

(b) The earth revolving around the sun. 

(c) A train moving along the equator of the earth in clockwise direction. 

(d) Accelerated motion of a particle in a straight line.

Define distance.

Define displacement.

Can magnitude of displacement be greater than distance travelled by particle?

A body is thrown with a velocity of 9.8 m/s in the vertical upward direction. What is the velocity after one second?

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